This invention relates to medico-surgical tubes and methods of manufacture.
The invention is more particularly concerned with tubes with a soft tip, and with methods of manufacture of such tubes.
It is often desirable for medico-surgical tubes, or catheters, to have a soft tip, so as to reduce trauma caused when the tip contacts patient tissue. In epidural catheters, a soft tip reduces the risk that the catheter will damage the dura. Various arrangements have been proposed for providing a soft tip, such as by attaching or moulding onto the shaft of the catheter a separate component of a softer material. Such an arrangement is not entirely satisfactory because a separate assembly operation is needed to form the tip, leading to increased manufacturing expense. Also, there is always some risk that a separate component might become detached from the body of the catheter. Other arrangements in which the rear part of the catheter is reinforced can also be difficult to make by automated assembly, thereby making the catheter relatively expensive. GB9906349 describes a catheter with a soft tip formed by extruding a tube with an inner layer of stiffer material, which is periodically interrupted to provide more flexible regions. In WO 94/01160 there is described an epidural catheter where an inner tube is preformed and then an outer tube is provided around it extending beyond the inner tube to form a less stiff region.
It is an object of the present invention to provide an alternative medico-surgical tube and method of manufacture of a such a tube.
According to one aspect of the present invention there is provided a medico-surgical tube having an inner layer and an outer layer, a part at least of the inner layer being removed from one end of tube such as to reduce the stiffness of the tube at the one end.
The tube may have an interlayer, such as of polyethylene, between the inner and outer layers preventing bonding between the inner and outer layers and enabling the part of the inner layer to be pulled from the one end of the tube. The tube is preferably closed at the one end and has a side opening towards the one end. The inner layer is preferably stiffer than the outer layer.
According to another aspect of the present invention there is provided a method of making a medico-surgical tube including the steps of forming a tubular member with an inner and outer layer, and subsequently removing a part at least of the inner layer along a region at one end of the tube such as to reduce the stiffness of the tube along the region.
The part of the inner layer may be removed by machining away the part of the inner layer along the region. The part of the inner layer may be machined away using a machine having a rotating milling head with a milling surface on an end face. Alternatively, the part of the inner layer may be removed by cutting away the part from the remainder of the inner layer and pulling it out of the tube. The part of the inner layer may be cut away using a machine having a rotating spindle carrying a radially-extending knife blade. Preferably the tube has an interlayer, such as of polyethylene, between the inner and outer layers preventing bonding between the inner and outer layers. The inner layer may be of a stiffer material than the outer layer. The outer layer is preferably end formed after removal of the part of the inner layer to close the one end of the tube, a side opening being formed in the tube towards the one end.
According to a further aspect of the present invention there is provided a medico-surgical tube made by a method according to the above other aspect of the invention.
According to a fourth aspect of the present invention there is provided a machine for use in the method according to the above other aspect of the invention.